June 1, 2015: Equine Encephalitides
June 1, 2015
The summer and fall seasons in North America herald outbreaks of viral zoonotic encephalitis. An important subset of infectious agents includes the equine encephalitides: Eastern, Western, and Venezuelan equine encephalitis. There geographic distribution is broad, with human cases of Eastern equine encephalitis reported in the East Coast, Gulf Coast, Midwest, and Texas; cases of Western equine encephalitis reported in Florida and most states west of the Mississippi; and, cases of Venezuelan equine encephalitis reported primarily in Central and South America(1). The equine encephalitides are a rare cause of disease in humans, with Eastern equine encephalitis being the most common and most virulent in the United States, with the mortality rate approaching 35%(1). Symptoms are nonspecific and include fever, malaise and myalgia beginning three to 10 days after a mosquito exposure, and progressing to headache, confusion, and seizures. Treatment is primarily supportive, with consideration of corticosteroids and anticonvulsants when indicated(2). Cases are confirmed with serum and CSF serologies(2).
- Go YY, Balasuriya UB, Lee CK. Zoonotic encephalitides caused by arboviruses: transmission and epidemiology of alphaviruses and flaviviruses. Clinical and Experimental Vaccine Research 2014; 3: 58-77.
- Davis LE, Beckham JD, Tyler KL. North America encephalitic arboviruses. Neurologic Clinics 2008; 26: 727-757.
Submitted by Adam Numis, MD, Department of Neurology, University of California, Los Angeles.
Disclosures: Dr. Numis is a member of the Residents & Fellows Section of Neurology.